Typical implantable medical devices, such as pacemakers and implantable cardioverter defibrillators, are designed with two or more housing components or shells that contain the control electronics, power source, and other device specific components. A header is also used to provide electrical connections into and out of the device. The housing and header (or feedthrough) are designed to be hermetic to prevent liquid or gas exchange between the internal components (which are typically not biocompatible) and body fluids. It is noted, however, that certain implants with epoxy based headers do not achieve long term hermeticity. Design and manufacturing methods of implantable devices have evolved with the goal of ensuring hermeticity.
MicroCHIPS Inc. designs and manufactures implantable devices based on microchips that include reservoir arrays containing biosensors or drugs, for example. FIG. 1 shows a possible conventional approach for assembly of components in an implantable medical device 10, which includes a microchip assembly 12. The microchip assembly 12, which is also referred to as a microchip element, includes microreservoirs, each of which may contain a drug for controlled delivery in vivo or a sensor for controlled exposure in vivo. The microchip assembly 12 is attached to a feedthrough 16 that is welded to the housing 14. Such microchip assemblies or elements are described, for example, in U.S. Pat. No. 7,510,551 to Uhland et al. and U.S. Pat. No. 7,604,628 to Santini Jr. et al. The feedthrough 16 contains electrically conductive pins that are metallurgically brazed to metallized surfaces on and through an alumina disc. A typical pin count exceeds 100, and in more complex designs, can be over 400. The consequence of such designs is that each pin connection potentially can be a leak point.
In addition, each feedthrough pin is electrically connected to an electronic component inside the housing. Some designs utilize a wire from the pin to the circuit, while the illustrated design attaches the feedthrough 16 directly to a conventional plastic circuit board 18 (which generally would be unsuitable for continuous in vivo contact with the patient). These electrical connections require testing to ensure continuity. As a result, the pin count impacts the cost of the feedthrough, and that cost increases as the number of feedthrough pins increases in the implantable device. Consequently, due to this complex design requirement, the resulting manufacturing, and the required acceptance tests, the feedthrough is a relatively expensive component.
Another disadvantage of conventional implantable device designs based on a feedthrough or header attached to housing components is that the overall volume of the resulting device is larger than ideally desired, because several discrete components make up the assembly.
Furthermore, electronic-based implantable devices that use radio frequency to wirelessly transfer information in and out of the body require an antenna. Radio frequency waves are significantly attenuated when the antenna is placed in a conventional metallic housing, and therefore, the antenna typically is placed on the surface of the housing, utilizing the existing feedthrough or another feedthrough dedicated for this application.
It therefore would be desirable to eliminate or mitigate any or all of the foregoing disadvantages associated with conventional designs of implantable medical devices. In one particular need, it would be desirable to provide improved housing hermeticity (e.g., fewer potential leak paths), simpler construction, and a smaller overall device volume.
In conjunction with the desire to provide improved hermetic reservoir devices, it would also be advantageous to improve the manner in which such actively-controlled reservoir devices can be operably deployed into a patient in need thereof. For example, it would be desirable to reduce the size of incisions and/or increase the possible range of tissue sites into which the device can be suitably deployed without undue pain or discomfort to the patient. It would be desirable to provide device configurations conducive to such uses in patients.